1. Field of the Invention
The present invention relates to battery power measuring systems and methods, and particularly to a battery power measuring system and method for a Battery-Backed SRAM (Static Random Access Memory).
2. Background of the Invention
A RAM (Random Access Memory) is one of the most important components in a typical computer, and is controlled by a CPU (Central Processing Unit). The close relationship between the RAM and the CPU is akin to the relationship between thinking and memory in a human. Data and instructions which are to be processed or are being processed by the CPU are stored in the RAM. The RAM is a volatile memory. That is, the RAM depends on ongoing electrical power to enable it to store data. The data is lost when there is no electrical power supplied to the RAM. Therefore, a so-called Battery-Backed SRAM (Static Random Access Memory) is becoming increasing popular. The Battery-Backed SRAM guarantees a continuous source of electrical power by supplying battery power in the event that a primary power source fails or is unavailable. The Battery-Backed SRAM is comprised of an SRAM and an internal battery. The Battery-Backed SRAM generally receives electrical power from the primary power source, and occasionally receives electrical power from the internal battery when the primary power source fails or becomes unavailable.
The power of the internal battery is limited. Knowing the exact amount of power remaining in the internal battery is critical to guaranteeing reliability of the Battery-Backed SRAM. There are many means for measuring the length of time that a battery's power will last before it runs out. This length of time is referred to herein as “endurance. ” Many of said means measure remaining endurance based on input received from detection devices or detection circuits. For example, China Pat. No. 1063769 issued on Aug. 19, 1992 and entitled “Battery Power Monitor For Personal Computer ” discloses a processor that receives and processes parameters from detection devices, and then measures remaining battery power according to a preset battery power table. The parameters include battery current, battery voltage, and battery temperature. The preset battery power table provides a remaining battery power value based on the received battery current, battery voltage and battery temperature. In another example, Taiwan Pat. No. 0911118 Sep. 21, 2003 and entitled “Methods And Systems For Noticing Battery Power Deficiency On Portable Electrical Device ” discloses a special circuit to determine a battery voltage. The circuit compares the battery voltage with a threshold voltage, and notifies users if the battery voltage is lower than the threshold voltage.
The monitor of the above China patent needs current detection circuits, voltage detection circuits and temperature detection circuits, and the methods and systems of the above Taiwan patent need special circuitry and logistic transistors. All these means require the addition of electronic control devices to the battery. These additional components increase the respective system's design, development and implementation costs, as well as the ultimate cost of the product to the customer. Furthermore, such hardware specific means are not easily transported from one platform and computer system to another without major redesign. In other words, the solutions lack portability. A battery power measuring system and method for a Battery-Backed SRAM which can overcome the above-mentioned problems is desired.